- serum urea concentration > 40 mmol / l serum potassium concentration > 6 mmol /L, serum potassium concentration > 5.5 mmol /L that persists despite well-conducted medical treatment with at least sodium bicarbonate and / or glucose-insulin infusion, arterial pH < 7.15 in the context of pure metabolic acidosis (PaCO2 <35 mmHg) or in the context of mixed acidosis with PaCO2> 50 mmHg without possibility of lowering this PaCO2 value, acute overload pulmonary edema generating severe hypoxemia requiring oxygen flow> 5L/min in spontaneously breathing patients or FiO2> 50% in mechanically (invasive or noninvasive) ventilated to maintain SpO2> 95%, despite diuretic therapy.